Clients suffering lower back pain, often commenting that it’s worse when they go from sitting to standing frequently turns out to be the psoas muscle in spasm.
The psoas (with a silent “P”) runs from the inside of the transverse processes of your lumbar vertebrae (the attachment surfaces of the bones of your lower spine) internally to the lesser trochanter of your femur (an attachment point on the inside of the top of your thigh bone) and acts as a hip flexor (raises your knee towards your chest) and external rotator (turns your thigh out).
When you are in a seated position it is in a shortened state, thus it often produces pain in the lower back when you stand and stretch it out.The muscle also interacts with other muscles and it is important to address these when releasing the psoas. It is commonly associated with the iliacus muscle that runs from the inside of the iliac crest (the hip bone) and attaches at the same point on the femur, the two together being known as the iliopsoas. However, it also interacts with the quadratus lumborum (a deeper muscle of the lower back) and the diaphragm, which is the muscle that helps to inflate your chest when you breath.
I’ve actually had patients come in with lower back pain after a particularly violent sneeze as the diaphragm has set off both the QL and the psoas.
For my money, the best treatment for this muscle is Bowen Therapy.
There is a simple tweak to the attachment at the upper thigh that uses the stretch receptors in the muscle and fascia to release it. As it is largely an internal muscle, it is very hard to massage. It always works better if the accompanying muscles are also tweaked.
There is also stretching to help release the muscle but it takes a little practice to get right. You need to kneel in a forward-leg lunge with the leg of the side you are stretching, back. Then lift the chest up away from the groin and lean slightly to the opposite side. This should produce a slight pull at the inner, upper thigh. For a more advanced stretch hold onto the back foot as shown here.